Protection monitoring circuit, battery pack, secondary battery monitoring circuit, and protection circuit

ABSTRACT

A protection monitoring circuit includes a protection circuit which detects overcharge, overdischarge, and overcurrent of a secondary battery, and a secondary battery monitoring circuit which monitors a state of the secondary battery and detects a residual quantity of the secondary battery. The protection circuit includes a first communication terminal that is connected to the secondary battery monitoring circuit, a second communication terminal that is connected to a mobile device, and a level shift circuit that is connected to the first and second communication terminals. The level shift circuit performs a level shift of a signal input of the first communication terminal so as to become a second level and outputs the signal to the second communication terminal, and also performs the level shift of a signal input of the second communication terminal so as to become a first level and outputs the signal to the first communication terminal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation patent application of, and claims thebenefit of and priority to U.S. patent application Ser. No. 13/143,844filed on Jul. 8, 2011, which is a National Phase application under 35U.S.C. 371 of PCT/JP2010/050357 filed on Jan. 14, 2010, which is basedon and claims the benefit of priority of Japanese Patent Application No.2009-006158, filed on Jan. 14, 2009, and Japanese Patent Application No.2010-005981, filed on Jan. 14, 2010, with the Japanese Patent Office,all of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a protection monitoring circuit, abattery pack, a secondary battery monitoring circuit, and a protectioncircuit.

BACKGROUND ART

In recent years, lithium ion batteries are installed in mobile devices,such as a digital camera and a cellular phone, as a secondary battery.Generally, lithium ion batteries are prone to overcharge, overdischargeand overcurrent, and a lithium ion battery is arranged in a form of abattery pack containing a protection circuit which detects overcharge,overcurrent and overdischarge of the battery to protect the battery frombeing damaged.

In a battery pack, a secondary battery monitoring circuit may becontained. This secondary battery monitoring circuit includes atemperature sensor which is arranged to detect a voltage change,corresponding to a temperature change in the battery pack, to determinea state of a lithium ion battery, such as a battery residual quantity.In this case, an additional communication terminal for transmitting anoutput signal from the secondary battery monitoring circuit to a mobiledevice is disposed in the battery pack, and the secondary batterymonitoring circuit receives the signal indicating the state of thebattery pack output from this communication terminal, and manages theoperating state of the battery pack.

Conventionally, a charging device which receives a control signal forcontrolling charging of a battery pack from a communication terminaldisposed in the battery pack is known. For example, refer to PatentDocument 1 listed below.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-209788

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, each of a protection circuit and a secondary battery monitoringcircuit, disposed in a battery pack according to the related art, doesnot include a communication part for communicating with each other, eachof these circuits may operate independently, and the secondary batterymonitoring circuit does not include a unit for detecting performance ofa protecting operation of the protection circuit.

Therefore, in order to determine whether the protection circuit isoperated, the secondary battery monitoring circuit has to monitor theoutput of a voltage sensor and the output of a current sensor disposedin the secondary battery monitoring circuit.

In order to determine whether the result of the monitoring meets thestate of the protection circuit for allowing the protecting operation,it is necessary for the secondary battery monitoring circuit tocontinuously perform the computations.

On the other hand, when determining performance of a protectingoperation by the protection circuit based on the computations of thesecondary battery monitoring circuit, there are the following problems.Performance of overcharge protecting operation by the protection circuitcan be properly determined by monitoring the power supply voltage.However, performance of overdischarge protecting operation by theprotection circuit is usually determined by detection of a power-onreset operation. Specifically, at a voltage in a vicinity ofoverdischarge detection voltage, supply of the power supply voltage tothe secondary battery monitoring circuit is inhibited, and it isnecessary to detect whether the supply of the power supply voltage tothe secondary battery monitoring circuit is restarted. In this case,there is a possibility of erroneous detection, and it is difficult toaccurately determine whether the protection circuit has been operated.

Also with respect to performance of an overcurrent protecting operationand performance of a short circuit protecting operation, it is verydifficult to determine whether the protection circuit has been operated.The value of an overcurrent detection current of the protection circuitis out of the range of the current that can be measured by the secondarybattery monitoring circuit, and the delay time up to the overcurrentdetection of the protection circuit is very short. The protectioncircuit may operate before the secondary battery monitoring circuitcompletes the current measurement, and it is difficult to measure thecurrent value.

Therefore, in order to store an accurate operating state of theprotection circuit into the secondary battery monitoring circuit, it isnecessary to provide a certain notification mechanism.

Furthermore, it is also necessary to provide a duplicate protectionfunction for increased safety by compulsively operating the protectioncircuit by the secondary battery monitoring circuit based on informationof the overcharge or the overcurrent of the secondary battery detectedby the secondary battery monitoring circuit.

Accordingly, in one aspect, the present disclosure a protectionmonitoring circuit, a battery pack, a secondary battery monitoringcircuit, and a protection circuit, which are adapted to allow thesecondary battery monitoring circuit to operate a protecting function ofthe protection circuit, allow the secondary battery monitoring circuitto request receiving of an operating state of the protection circuitfrom the protection circuit, and allow the protection circuit to send anoperating state of the protection circuit to the secondary batterymonitoring circuit.

Means to Solve the Problem

In an embodiment which solves or reduces one or more of theabove-described problems, the present disclosure provides a protectionmonitoring circuit (101) including: a secondary battery monitoringcircuit (120) which detects a state of a chargeable and dischargeablesecondary battery (110); and a protection circuit (130) which performsan ON/OFF control of a charge control transistor or a discharge controltransistor (M11, M12) disposed between the secondary battery (110) and aload or a charger device, and protects the secondary battery (110),wherein the secondary battery monitoring circuit (120) outputs a controlsignal that compulsively turns on/off the charge control transistor orthe discharge control transistor (M11, M12), to the protection circuit(130), and the protection circuit (130) performs the ON/OFF control ofthe charge control transistor or the discharge control transistor uponreceipt of the control signal.

The protection monitoring circuit (101) of the present disclosure may bearranged so that the the secondary battery monitoring circuit (120)detects at least one of overcharge, overdischarge, and overcurrent ofthe secondary battery (110), and when the at least one of overcharge,overdischarge, and overcurrent of the secondary battery (110) isdetected, the secondary battery monitoring circuit outputs a controlsignal that compulsively turns off the charge control transistor or thedischarge control transistor, to the protection circuit (130), and theprotection circuit (130) performs an OFF control of the charge controltransistor or the discharge control transistor upon receipt of thecompulsive turn-off control signal.

The protection monitoring circuit (101) of the present disclosure may bearranged so that respective thresholds that are predetermined for theprotection circuit (130) to detect overcharge, overdischarge, andovercurrent of the secondary battery (110) are different from respectivethresholds that are predetermined for the secondary battery monitoringcircuit (120) to detect overcharge, overdischarge, and overcurrent ofthe secondary battery (110).

The protection monitoring circuit (101) of the present disclosure may bearranged so that the secondary battery monitoring circuit (120) outputsan operating state inquiry signal that requests receiving of anoperating state of the protection circuit (130), to the protectioncircuit (130), and, when the inquiry signal is received, the protectioncircuit (130) outputs a notification signal that indicates the operatingstate of the protection circuit, to the secondary battery monitoringcircuit (120).

The protection monitoring circuit (101) of the present disclosure may bearranged so that, when at least one of overcharge, overdischarge, andovercurrent of the secondary battery (110) is detected, the protectioncircuit (130) outputs a notification signal that indicates thedetection, to the secondary battery monitoring circuit (120), and thesecondary battery monitoring circuit (120) includes a nonvolatile memory(124), and stores information that indicates the detection or theoperating state, in the nonvolatile memory (124) when the notificationsignal or the operating state notification signal is received.

The protection monitoring circuit (101) of the present disclosure may bearranged so that the secondary battery monitoring circuit (120) countsthe number of times of detection for each of overcharge, overdischarge,and overcurrent of the secondary battery (110) in response to thenotification signal or the operating state notification signal received,and stores the counted number of times of detection for each ofovercharge, overdischarge, and overcurrent of the secondary battery inthe nonvolatile memory (124).

The protection monitoring circuit (101) of the present disclosure may bearranged so that, when one of the counted numbers of times of detectionexceeds a corresponding one of predetermined numbers of times for eachof overcharge, overdischarge, and overcurrent of the secondary battery(110), the secondary battery monitoring circuit (120) outputs a controlsignal that compulsively turns off the charge control transistor or thedischarge control transistor, to the protection circuit (130) based on aresult of the detection.

The protection monitoring circuit (101) of the present disclosure may bearranged so that the protection circuit (130) includes a firstcommunication terminal (152) connected to the secondary batterymonitoring circuit (120), a second communication terminal (153)connected to a communication terminal (116) coupled to the load, and acircuit which connects the first communication terminal (152) and thesecond communication terminal (153) together, and the circuit isarranged to pass through a signal transmitted between the secondarybattery monitoring circuit (120) and the load.

The protection monitoring circuit (101) of the present disclosure may bearranged to further include a resistor (R4) which is connected betweenthe communication terminal (116) coupled to the load and the secondcommunication terminal (153).

Furthermore, the present disclosure provides a battery pack (100) inwhich the above-described protection monitoring circuit (101) isarranged.

In an embodiment which solves or reduces one or more of theabove-described problems, the present disclosure provides a secondarybattery monitoring circuit (120) which detects a state of a chargeableand dischargeable secondary battery (110) and is connected to aprotection circuit (130) which detects at least one of overcharge,overdischarge, and overcurrent of the secondary battery (110) andperforms an ON/OFF control of a charge control transistor or a dischargecontrol transistor disposed between the secondary battery and a load ora charger device, to protect the secondary battery, wherein thesecondary battery monitoring circuit (120) is arranged to output acontrol signal that compulsively turns on/off the charge controltransistor or the discharge control transistor, to the protectioncircuit (130).

The secondary battery monitoring circuit (120) of the present disclosuremay be arranged so that the secondary battery monitoring circuit outputsa control signal that compulsively turns off the charge controltransistor or the discharge control transistor, to the protectioncircuit (130) when at least one of overcharge, overdischarge, andovercurrent of the secondary battery (110) is detected.

The secondary battery monitoring circuit (120) of the present disclosuremay be arranged so that the secondary battery monitoring circuitincludes a nonvolatile memory (124), and when an operating statenotification signal indicating an operating state of the protectioncircuit (30) is received from the protection circuit (130), or when anotification signal indicating that at least one of overcharge,overdischarge, and overcurrent of the secondary battery (110) isdetected is received from the protection circuit (130), the secondarybattery monitoring circuit stores information that indicates thedetection by the protection circuit or the operating state of theprotection circuit, in the nonvolatile memory (124).

The secondary battery monitoring circuit (120) of the present disclosuremay be arranged so that the secondary battery monitoring circuit countsthe number of times of detection for each of overcharge, overdischarge,and overcurrent of the secondary battery (110) in response to thenotification signal or the operating state notification signal received,and stores the counted number of times of detection for each ofovercharge, overdischarge, and overcurrent of the secondary battery inthe nonvolatile memory (124), and, when one of the counted numbers oftimes of detection exceeds a corresponding one of predetermined numbersof times for each of overcharge, overdischarge, and overcurrent of thesecondary battery, the secondary battery monitoring circuit outputs acontrol signal that compulsively turns off the charge control transistoror the discharge control transistor, to the protection circuit (130)based on a result of the detection.

In an embodiment which solves or reduces one or more of theabove-described problems, the present disclosure provides a protectioncircuit (130) which is connected to a secondary battery monitoringcircuit (120), which detects a state of a chargeable and dischargeablesecondary battery (110) and has a nonvolatile memory (124) which storesa control state by the protection circuit, wherein the protectioncircuit (130) detects at least one of overcharge, overdischarge, andovercurrent of the secondary battery (110) and performs an ON/OFFcontrol of a charge control transistor or a discharge control transistordisposed between the secondary battery (110) and a load or a chargerdevice to protect the secondary battery (110), and wherein theprotection circuit performs the ON/OFF control of the charge controltransistor or the discharge control transistor when a control signalthat compulsively turns on/off the charge control transistor or thedischarge control transistor is received from the secondary batterymonitoring circuit (120).

The protection circuit (130) of the present disclosure may be arrangedto output a notification signal indicating that the at least one ofovercharge, overdischarge, and overcurrent of the secondary battery(110) is detected, to the secondary battery monitoring circuit (120).

It is to be understood that the reference numerals in parentheses in theforegoing general description are exemplary and explanatory and notrestrictive of the present disclosure.

Effect of the Invention

According to the present disclosure, the secondary battery monitoringcircuit can operate a protecting function of the protection circuit, thesecondary battery monitoring circuit can request receiving of anoperating state of the protection circuit from the protection circuit,and the protection circuit can send an operating state of the protectioncircuit to the secondary battery monitoring circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the composition of a battery pack of anembodiment of the present disclosure.

FIG. 2 is a diagram showing the hardware composition of a secondarybattery monitoring IC.

FIG. 3 is a diagram showing the internal composition of a protection IC.

FIG. 4 is a diagram showing a condition in which a charger device isreversely connected to an external terminal.

FIG. 5 is a diagram showing a signal output from the secondary batterymonitoring IC to the protection IC of this embodiment.

FIG. 6 is a diagram showing a list of commands recognized by theprotection IC.

FIG. 7 is a diagram showing a notification command of a protectingdetection state of the protection IC sent to the secondary batterymonitoring IC.

FIG. 8 is a diagram for explaining the operation at a time of thecommunication from the protection IC to the secondary battery monitoringIC when a state of the secondary battery other than overdischarge isdetected by the protection IC.

FIG. 9 is a diagram for explaining the operation at a time of thecommunication from the protection IC to the secondary battery monitoringIC when overdischarge of the secondary battery is detected by theprotection IC.

FIG. 10 is a diagram showing a list of commands recognized by thesecondary battery monitoring IC.

FIG. 11 is a diagram showing an example of a mobile device in which abattery pack including a protection monitoring circuit of thisembodiment is arranged.

BEST MODE FOR CARRYING OUT THE INVENTION

A description will be given of embodiments of the present disclosurewith reference to the accompanying drawings.

<Internal Composition of Battery Pack>

FIG. 1 is a diagram showing the composition of a battery pack of anembodiment of the present disclosure.

As shown in FIG. 1, the battery pack 100 is constructed to include aprotection monitoring circuit 101 and a battery unit 111. The protectionmonitoring circuit 101 and the battery unit 111 are connected togetherby a secondary battery positive terminal 112 and a secondary batterynegative terminal 113.

The protection monitoring circuit 101 includes a secondary batterymonitoring IC 120, a protection IC 130, resistors R1-R5, capacitorsC1-C3, a MOS (metal oxide semiconductor) transistor M11 having aparasitism diode D1, a MOS transistor M12 having a parasitism diode D2,a positive terminal 114, a negative terminal 115, and an externalterminal 116 which are disposed on a single substrate and constructedinto a protection module or a COB (chip on board) module. The secondarybattery monitoring circuit and the protection circuit may be constructedby an IC (integrated circuit), or may be provided in the form of, forexample, an IC package or a COB module.

The battery pack 100 is connected to a mobile device, a charging device,etc. by the positive terminal 114 and the negative terminal 115. Thebattery pack 100 monitors a state of a battery unit 111 which includestwo or more secondary batteries 110, by using the secondary batterymonitoring IC 120, and protects the battery unit 111 from overcharge,overcurrent, overdischarge, etc. by using the protection IC 130.

<Secondary Battery Monitoring IC 120>

Next, the secondary battery monitoring IC 120 shown in FIG. 1 will bedescribed.

The secondary battery monitoring IC 120 monitors a state of the batteryunit 111, acquires the state information of the battery unit 111, anddetects a residual quantity of the battery and other information. Thesecondary battery monitoring IC 120 sends the acquired state informationto the mobile device when a request for accessing the state informationis received from the mobile device. For example, the product name MM8002is attached to the secondary battery monitoring IC 120.

The secondary battery monitoring IC 120 is constructed to include a VDD1terminal which is a power-supply terminal, a VSS terminal which is areference potential terminal, a VBAT1 terminal which is a voltagedetection terminal of the battery unit 111, a VRSP terminal and a VRSMterminal which are a set of voltage detection terminals to detect avoltage between the ends of a resistor R3, an SIO terminal which is acommunication terminal with the mobile device, a PORT0 terminal which isa communication terminal with the protection IC 130, a PORT1 terminal,and a PORT2 terminal.

The power supply voltage from the protection IC 130 is regulated(stabilized) and the regulated power supply voltage is supplied to thesecondary battery monitoring IC 120 via the VDD1 terminal which is thepower-supply terminal. The value of the power supply voltage suppliedfrom the protection IC 130 is set to a voltage value which is lower thana predetermined value of the power supply voltage of the battery unit111 which is detected as overdischarge of the battery. The secondarybattery monitoring IC 120 is controlled to operate appropriately underthe value of the power supply voltage which is set up in this way.

The secondary battery monitoring IC 120 detects a power supply voltageof the battery unit 111 through the VBAT1 terminal which is the voltagedetection terminal connected to the position terminal of the batteryunit 111. The VRSM and VRSP terminals which are the set of voltagedetection terminals are to detect the voltage between the ends of theresistor R3 which is disposed outside the secondary battery monitoringIC 120, and thereby detect the current flowing through the resistor R3.Hence, the secondary battery monitoring IC 120 detects thecharging/discharge current of the battery unit 111.

The SIO terminal of the secondary battery monitoring IC 120 is connectedthrough the protection IC 130 to the external terminal 116 which is usedfor communication with the mobile device. The secondary batterymonitoring IC 120 performs communication with the mobile device throughthe SIO terminal (which is the communication terminal) and theprotection IC 130.

The secondary battery monitoring IC 120 performs communication with theprotection IC 130 through the PORT0 terminal, the PORT1 terminal, andthe PORT2 terminal, which are the communication terminals connected tothe protection IC 130.

For example, the secondary battery monitoring IC 120 outputs, to theprotection IC via the PORT0 terminal, the PORT1 terminal and the PORT2terminal, a control signal for compulsively turning off or compulsivelyturning on the MOS transistors M11 and M12 which are the dischargecontrol transistor and the charge control transistor of the protectionIC 130.

Specifically, when it is detected that the battery voltage of thebattery unit 111 is higher than a predetermined overcharge detectionvoltage value, a charge control signal for compulsively turning off theMOS transistor M12 (the charge control transistor) is output to theprotection IC 130. When it is detected that the battery voltage of thebattery unit 111 is lower than a predetermined overdischarge detectionvoltage value, the secondary battery monitoring IC 120 outputs adischarge control signal for compulsively turning off the MOS transistorM11 (the discharge control transistor), to the protection IC 130.

When it is detected that the charging current of the battery unit 111 ishigher than a predetermined charge overcurrent detection current value,the secondary battery monitoring IC 120 outputs a charge control signalfor compulsively turning off the MOS transistor M12 (the charge controltransistor) to the protection IC 130. When it is detected that thedischarge current of the battery unit 111 is lower than a predetermineddischarge overcurrent value, the secondary battery monitoring IC 120outputs a discharge control signal for compulsively turning off the MOStransistor M11 (the discharge control transistor) to the protection IC130.

The secondary battery monitoring IC 120 outputs an operating stateinquiry signal that requests receiving of an operating state of theprotection IC 130, to the protection IC 130, and receives from theprotection IC 130 a notification signal that indicates the operatingstate of the protection IC 130 in response to the inquiry signal. Thesecondary battery monitoring IC 120 receives from the protection IC 130a notification signal indicating that any of overcharge, overdischarge,charge overcurrent and discharge overcurrent of the secondary batteryhas been detected.

The secondary battery monitoring IC 120 stores the informationindicating the operating state of the protection IC 130 in thenonvolatile memory based on the operating state notification signalreceived from the protection IC 130, or stores in the nonvolatile memorythe information indicating the detection of any of overcharge,overdischarge, charge overcurrent and discharge overcurrent of thesecondary battery, based on the notification signal received from theprotection IC 130.

<Protection IC 130>

Next, the protection IC 130 shown in FIG. 1 will be described. Theprotection IC 130 includes an overcharge detection circuit, anovercurrent detection circuit, and an overdischarge detection circuitwhich are built in the protection IC 130, and detects overcharge,overcurrent, and overdischarge of the battery unit 111, to protect thebattery unit 111 from overcharge, overcurrent, and overdischarge. Forexample, the product name MM3289 is attached to the protection IC 130.

The protection IC 130 is constructed to include a VDD2 terminal which isa power-supply terminal, a VSS terminal which is a reference potentialterminal, a VSENSE terminal which is a voltage detection terminal, and aVREGOUT terminal which is a terminal which outputs the regulated voltageto the secondary battery monitoring IC 120.

The protection IC 130 is constructed to include a DOUT terminal, a COUTterminal, a CCNT terminal, a DCNT terminal, and an INT terminal. TheDOUT and COUNT terminals are respectively connected to the gates of theMOS transistors M11 and M12 which are used to inhibit the charging anddischarging of the battery pack 100. The CCNT, DCNT and INT terminalsare communication terminals with the secondary battery monitoring IC120.

The power supply voltage is supplied to the protection IC 130 throughthe VDD2 terminal which is the power-supply terminal connected to theposition terminal of the battery unit 111. The VSS terminal which is thereference potential terminal is connected to the negative electrode ofthe battery unit 111.

The protection IC 130 includes a voltage regulator (LDO) 131 whichperforms a low saturation regulation. The power supply voltage suppliedto the VDD2 terminal is regulated by the voltage regulator 131, and theregulated power supply voltage is supplied to the secondary batterymonitoring IC 120 via the VREGOUT terminal. The value of the powersupply voltage (the output voltage of the voltage regulator 131) whichis regulated by the voltage regulator 131 and supplied to the secondarybattery monitoring IC 120 is set up to be lower than a predeterminedvalue of the power supply voltage of the battery unit 111 that isdetected as overdischarge. The secondary battery monitoring IC 120 iscontrolled to operate appropriately under the value of the power supplyvoltage which is set up in this way.

When the value of the power supply voltage of the battery unit 111 islowered, such as in a case where overdischarge of the battery unit 111is detected, the value of the power supply voltage supplied to thesecondary battery monitoring IC 120 is also lowered. Hence, if the valueof the power supply voltage for the secondary battery monitoring IC 120to operate normally is set up to be higher than the predetermined valueof the power supply voltage and overdischarge of the battery unit 111 isdetected, then the power supply voltage for the secondary batterymonitoring IC 120 to operate normally is not supplied. In this case, theoperating state of the secondary battery monitoring IC 120 may beunstable. Although the secondary battery monitoring IC 120 has thefunction of monitoring the state of the power supply voltage of thebattery unit 111, the state of the battery unit 111 cannot be accuratelydetected by the secondary battery monitoring IC 120 which is in theunstable operating state.

However, in this embodiment, the value of the regulated power supplyvoltage being supplied to the secondary battery monitoring IC 120 is setup to be lower than the predetermined value of the power supply voltageof the battery unit 111 that is detected as overdischarge. Hence, thesecondary battery monitoring IC 120 is controlled to operateappropriately.

When the value of the regulated power supply voltage being supplied tothe secondary battery monitoring IC 120 is lowered due to lowering ofthe power supply voltage of the battery unit 111, overdischarge of thebattery unit 111 is first detected, and the supply of the power supplyvoltage to the secondary battery monitoring IC 120 is inhibited asdescribed above. Hence, even if the power supply voltage of the batteryunit 111 is lowered to a value in the vicinity of the overdischargedetection voltage of the protection IC 130, it is possible to preventthe power supply voltage supplied to the secondary battery monitoring IC120 from being lowered. Therefore, the secondary battery monitoring IC120 can normally store the log information of the state of the batteryunit 111 before overdischarge of the battery unit 111 is detected.

In this embodiment, the voltage regulator 131 and the protection IC 130are arranged in a unitary composition and integrated on the substrate.The present disclosure is not limited to this embodiment. Alternatively,the voltage regulator 131 and the protection IC 130 may be arrangedseparately on different substrates.

The protection IC 130 detects a power supply voltage of the battery unit111 through the VSENSE terminal which is the voltage detection terminalconnected to the position terminal of the battery unit 111. The VSENSEterminal is used to detect overcharge of the battery unit 111 and toinput a voltage to the overdischarge detection circuit. Whenoverdischarge or overcurrent of the battery unit 111 is detected, theprotection IC 130 turns off the MOS transistor M11 by setting the outputof the DOUT terminal to a low level. When overcharge or chargeovercurrent of the battery unit 111 is detected, the protection IC 130turns off the MOS transistor M12 by setting the output of the COUTterminal to a low level.

The protection IC 130 performs communication with the secondary batterymonitoring IC 120 through the CCNT terminal, the DCNT terminal and theINT terminal, which are the communication terminals connected to thesecondary battery monitoring IC 120. Specifically, when one ofovercharge, overcurrent, and overdischarge of the battery unit 111 isdetected, the protection IC 130 outputs a notification signal indicatingthat the one of overcharge, overcurrent, and overdischarge of thebattery unit 111 is detected, to the secondary battery monitoring IC120.

When overdischarge of the battery unit 111 is detected, the protectionIC 130 turns off the voltage regulator 131 (shutdown) after apredetermined time has elapsed from the time of detection of the batteryoverdischarge or after a control signal for turning off the voltageregulator 131 (or a voltage regulator OFF signal) is received from thesecondary battery monitoring IC 120, and inhibits supply of the powersupply voltage to the secondary battery monitoring IC 120. At the sametime, the protection IC 130 is shifted to a shutdown mode.

After the protection IC 130 is shut down at the time of detection of thebattery overdischarge, charging of the secondary battery 111 isrestarted. When a predetermined voltage of the secondary battery 111 bythe charging is reached, the protection IC 130 determines that thesecondary battery 111 is returned to the normal state from theoverdischarge state, and turns on the voltage regulator 131.

In the present embodiment, the respective predetermined thresholds forthe protection IC 130 to detect overcharge, overdischarge, andovercurrent of the battery unit are different from the respectivepredetermined thresholds for the secondary battery monitoring IC 120 todetect overcharge, overdischarge, and overcurrent of the battery unit.Thereby, the protection monitoring circuit 101 can provide the doubledetection functions of the secondary battery monitoring IC 120 and theprotection IC 130 for detecting overcharge and other states of thebattery unit.

<Hardware Composition of Secondary Battery Monitoring IC 120>

Next, the secondary battery monitoring IC 120 will be described withreference to FIG. 2. FIG. 2 shows the hardware composition of thesecondary battery monitoring IC 120 of this embodiment.

As shown in FIG. 2, the secondary battery monitoring IC 120 isconstructed to include a CPU (central processing unit) 121, a sensorpart 122, a ROM (read only memory) 123, an EEPROM (electronicallyerasable and programmable ROM) 124, a serial interface (I/F) 125, and aninput/output port (I/O port) 126.

The CPU 121 controls respective parts of the secondary batterymonitoring IC 120. The sensor part 122 detects a voltage, a current, anda temperature of the battery unit 111. The ROM 123 stores a programexecuted by the CPU 121 to control the respective parts of the secondarybattery monitoring IC 120.

The CPU 121 generates a control signal sent to the protection IC 130,and outputs the generated control signal to the protection IC 130 viathe input/output port 126 from PORT0, PORT1, and PORT2 terminals whichare connected to the protection IC 130.

Specifically, when a notification signal indicating that the batteryoverdischarge is detected by the protection IC 130 is received from thePORT0, PORT1 and PORT2 terminals, the CPU 121 performs an interruptprocess to store the information indicating that the overdischarge isdetected by the protection IC 130 into the nonvolatile memory, such asthe EEPROM 124 or the like.

At this time, the CPU 121 stores the information indicating that theoverdischarge is detected. Immediately before stopping the operation(function) of the secondary battery monitoring IC 120, the CPU 121generates a voltage regulator OFF signal which is a control signal forturning off the voltage regulator 131 of the protection IC 130, andoutputs the generated signal to the protection IC 130 via the PORT0,PORT1 and PORT2 terminals.

For example, when the information indicating the detection of thebattery overdischarge is stored in the EEPROM 124, the CPU 121increments the number of times of detection by using a register, etc. tocount the number of times of detection and stores the counted number oftimes of detection in the EEPROM 124.

The EEPROM 124 stores information including respective parameters of thevoltage, the current and the temperature, etc. of the battery unit 111detected by the sensor part 122. The EEPROM 124 further stores theinformation indicating that one of overcharge, overcurrent andoverdischarge of the battery unit 111 is detected, which information isreceived via the input/output port 126 from the PORT0, PORT1 and PORT2terminals which are the three communication terminals.

The input/output port 126 is used to send or receive the signal forcommunicating with the protection IC 130, through the PORT0, PORT1 andPORT2 terminals which are the three communication terminals.

The CPU 121, the sensor part 122, the ROM 123, the EEPROM 124, theserial I/F 125, and the input/output port 126 are interconnected by abus 127 and data and programs can be exchanged between these components.

The sensor part 122 is constructed to include a temperature sensorcircuit 122 a, a voltage sensor circuit 122 b, a current sensor circuit122 c, a multiplexer 122 d, and an analog-to-digital (A/D) converter 122e.

The temperature sensor circuit 122 a detects a temperature of thebattery unit 111. The voltage sensor circuit 122 b detects an outputvoltage of the battery unit 111 via a voltage detection terminal VBAT1which is connected to the battery unit 111. The current sensor circuit122 c detects a current which flows through an external resistor R3,i.e., the charging and discharging current of the battery unit 111, viavoltage detection terminals VRSP and VRSM which are connected to theends of the external resistor R3.

The outputs of the temperature sensor circuit 122 a, the voltage sensorcircuit 122 b and the current sensor circuit 122 c are connected to themultiplexer 122 d, and the multiplexer 122 d outputs a single outputsignal. The A/D converter 122 e converts the analog signal output fromthe multiplexer 122 d into digital data.

<Outline of Internal Composition of Protection IC 130>

Next, with reference to FIG. 3, the outline of the internal compositionof the protection IC 130 will be described. FIG. 3 shows the outline ofthe internal composition of the protection IC.

As shown in FIG. 3, the protection IC 130 is constructed to include avoltage regulator (LDO) 131, an overcharge detection circuit 132, anoverdischarge detection circuit 133, an overcurrent detection circuit134, and a short-circuit detection circuit 135.

The protection IC 130 is constructed to include a logic circuit 136, adelay circuit 137, and a communication control circuit 138. The logiccircuit 136 generates a control signal based on a detection signalreceived from each of the above detection circuits and outputs thecontrol signal. The delay circuit 137 is a non-sensitive time settingcircuit. The communication control circuit 138 controls thebidirectional communication between the protection IC 130 and thesecondary battery monitoring IC 120.

As shown in FIG. 3, the protection IC 130 is constructed to include aVSS terminal 142, a VDD terminal 143, a DOUT terminal 144, a COUTterminal 145, a V−(minus) input terminal 146, a VREGOUT terminal 147, aVSENSE terminal 148, a CCNT terminal 149, a DCNT terminal 150, and anINT terminal 151.

The voltage regulator 131 is connected to the VDD terminal 143 (the VDD2terminal shown in FIG. 1) which is a power-supply terminal, and carriesout the regulation of the power supply voltage being supplied to theprotection IC 130. The voltage regulator 131 is connected to the VREGOUTterminal 147, regulates the power supply voltage, and outputs theregulated power supply voltage from the VREGOUT terminal 147 to thesecondary battery monitoring IC 120.

The overcharge detection circuit 132 includes a comparator. In theovercharge detection circuit 132, the non-inverted input terminal isconnected to a junction point between the resistors R11 and R12 whichare connected in series between the VSS terminal 142 and the VSENSEterminal 148, and the inverted input terminal is connected to thepositive electrode side of a reference voltage source Vref1.

The overdischarge detection circuit 133 includes a comparator similar tothe overcharge detection circuit 132. In the overdischarge detectioncircuit 133, the non-inverted input terminal is connected to a junctionpoint between the resistors R13 and R14 which are connected in seriesbetween the VSS terminal 142 and the VSENSE terminal 148. The invertedinput terminal of the overdischarge detection circuit 133 is connectedto the positive electrode side of the reference voltage source Vref1.

The overcurrent detection circuit 134 includes a comparator similar tothe overcharge detection circuit 132 or the overdischarge detectioncircuit 133. In the overcurrent detection circuit 134, the non-invertedinput terminal is connected to the V− input terminal 146 via theresistor R15, and the inverted input terminal is connected to thepositive electrode side of a reference voltage source Vref2. Thenegative electrode side of each of the reference voltage sources Vref1and Vref2 is connected to the VSS terminal 142.

The short-circuit detection circuit 135 includes an amplifier with ahysteresis function, and is connected to the V− input terminal 146 viathe resistor R15.

The overcharge detection circuit 132 outputs an overcharge detectionsignal when an overcharge state of the secondary battery is detected.The overdischarge detection circuit 133 outputs an overdischargedetection signal when an overdischarge state of the secondary battery isdetected, and outputs an overdischarge return signal when anoverdischarge recovery of the secondary battery is detected. Theovercurrent detection circuit 134 outputs an overcurrent detectionsignal when an overcurrent of the secondary battery is detected.

Outputting any one of the overcharge detection signal, the overdischargedetection signal and the overcurrent detection signal is maintainedwhile a corresponding one of the overcharge state, the overdischargestate and the overcurrent state of the secondary battery is continued,and each corresponding detection signal is input to the logic circuit136. When the corresponding one of the overcharge detection signal, theoverdischarge detection signal and the overcurrent detection signal isinput to the logic circuit 136, the logic circuit 136 outputs a signalaccording to each corresponding state to the delay circuit 137.

The delay circuit 137 outputs a first overdischarge designation signalto the logic circuit 136 when the signal corresponding to theoverdischarge detection signal is received from the logic circuit 136and a first-step non-sensitive time which is predetermined for theoverdischarge detection signal has elapsed. Further, the logic circuit136 outputs a second overdischarge designation signal to the logiccircuit 136 when a predetermined second-step non-sensitive time haselapsed.

The logic circuit 136 outputs a discharge control signal for cutting offthe discharging current to the DOUT terminal 144 via the inverter 140and the resistor R16 when the first overdischarge designation signaldescribed above is received. Further, the logic circuit 136 outputs avoltage-regulator OFF signal for turning off the voltage regulator 131to the voltage regulator 131 when the second overdischarge designationsignal described above is received.

The delay circuit 137 outputs an overcurrent designation signal to thelogic circuit 136 when the signal corresponding to the overcurrentdetection signal is received from the logic circuit 136 and anon-sensitive time which is predetermined for the overcurrent detectionsignal has elapsed. When the overcurrent designation signal is received,the logic circuit 136 outputs a discharge control signal for cutting offthe discharging current to the DOUT terminal 144.

The logic circuit 136 outputs a discharge control signal for cutting offthe discharging current to the DOUT terminal 144, without non-sensitivetime, when a short-circuit detection signal is received from theshort-circuit detection circuit 135.

The logic circuit 136 outputs a voltage regulator ON signal for turningon the voltage regulator 131 to the voltage regulator 131, withoutnon-sensitive time, when an overdischarge return signal is received fromthe overdischarge detection circuit 133.

The delay circuit 137 outputs an overcharge designation signal to thelogic circuit 136 when the signal corresponding to the overchargedetection signal is received from the logic circuit 136 and anon-sensitive time which is predetermined for the overcharge detectionsignal has elapsed. When the overcharge designation signal is received,the logic circuit 136 outputs a charge control signal for cutting offthe charging current to the COUT terminal 145 via the inverter 141 andthe resistor R17.

When a voltage regulator OFF signal for turning off the voltageregulator 131 is received from the secondary battery monitoring IC 120via one of the CCNT terminal 149, the DCNT terminal 150 and the INTterminal 151, the communication control circuit 138 outputs anotification signal indicating the shutdown of the voltage regulator 131to the logic circuit 136. The logic circuit 136 outputs a voltageregulator OFF signal to the voltage regulator 131 in response to thenotification signal indicating the shutdown of the voltage regulator 131and received from the communication control circuit 138.

When a corresponding one of the overcharge detection signal, theoverdischarge detection signal and the overcurrent detection signal isreceived at the logic circuit 136 as described above, the communicationcontrol circuit 138 outputs the corresponding one of the overchargedetection signal, the overdischarge detection signal and the overcurrentdetection signal to the secondary battery monitoring IC 120 via acorresponding one of the CCNT terminal 149, the DCNT terminal 150 andthe INT terminal 151.

The protection IC 130 is constructed to include an SIOI terminal 152connected to the secondary battery monitoring IC 120, a level shiftcircuit 139 to perform the level shifting of the communication pulsesignal output from the SIOI terminal 152, and an SIOE terminal 153connected to the external terminal 116 for performing communication witha mobile device, etc. The level shift circuit 139 shifts the level ofthe communication pulse signal indicating the state information andreceived from the SIOI terminal 152, and outputs the resulting signal.

The SIOI terminal 152 and the SIOE terminal 153 are used to merely passthrough the communication signal transmitted between the mobile deviceand the secondary battery monitoring IC 120. Specifically, if thevoltage of one of these terminals is set to a low level, the low-levelvoltage signal is output to the other terminal. The same operation isperformed for each of the bidirectional communication signals.

The secondary battery monitoring IC 120 is fabricated using a precisionIC manufacture process of a microcomputer-incorporated semiconductordevice (which is prone to static electricity), while the protection IC130 is fabricated using an IC manufacturing process and has goodresistance against static electricity and high voltage. Thecommunication terminals used to communicate with a mobile device arealso used as terminals of battery packs. It is necessary that thecommunication terminals meet the requirements of the safety standards ofbattery packs and have good resistance against static electricity andhigh voltage. However, if the communication terminals of the secondarybattery monitoring IC 120 are used without changes, it is difficult forthe communication terminals to meet the requirements for staticelectricity.

Therefore, in this embodiment, as described above, the protection IC 130is arranged into the circuit which passes the communication signaltransmitted between the SIOI terminal 152 connected to the SIO terminal(which is a communication terminal of the secondary battery monitoringIC 120) and the SIOE terminal 153 connected to the external terminal 116(which is a communication output terminal with the mobile device body).Thereby, the SIO terminal of the secondary battery monitoring IC 120receives the signal transmitted from the mobile device through theprotection IC 130, and is provided to be a communication terminal thatis strong against static electricity or high voltage.

In this embodiment, it is unnecessary to add static protectioncomponents, such as zener diodes, capacitors and resistors, in order toprotect breakage of the communication terminal of the secondary batterymonitoring IC 120, and the cost can be reduced and the substrate areacan be reduced.

In this embodiment, the external terminal 116 shown in FIG. 1 is acommunication terminal used by the secondary battery monitoring IC 120to communicate with the mobile device, and the external terminal 116 isa terminal for outputting and inputting the information exchangedbetween the battery pack 100 and the mobile device.

As shown in FIG. 1, the resistor R4 is connected between the externalterminal 116 and the SIOE terminal 153. An intermediate voltage betweenthe positive terminal 114 and the negative terminal 115 is alwaysapplied to the external terminal 116. Even when a charger device isreversely connected to the external terminal 116, the supplied currentis restricted by the resistor R4, and it is possible to prevent theprotection IC 130 from being damaged.

Next, a case in which a charger device is reversely connected to theexternal terminal 116 which is used as a communication terminal with themobile device will be described.

FIG. 4 is a diagram showing a condition in which the charger device isreversely connected to the external terminal. As shown in FIG. 4, whenthe plus terminal side of the charger device is connected to theexternal terminal 116 and the negative electrode side of the chargerdevice is connected to the positive terminal 114, the power supplydirection of the protection IC 130 is reversed. In such a case, as shownin FIG. 4, the protection IC 130 is arranged to function as aforward-direction diode. Hence, the maximum amount of the current fromthe charger device connected will continuously flow through theprotection IC 130, and there is a possibility that the protectionmonitoring circuit 101 will be heated by the supplied current.

However, in this embodiment, the resistor R4 having a resistance in arange between 1 kΩ and 10 kΩ is connected in series between the SIOEterminal 153 of the protection IC 130 and the external terminal 116, andthe supplied current is restricted by the resistor R4 and reduced to anamount that does not cause heating of the protection monitoring circuit101. Thereby, as described above, even in the case in which the chargerdevice is reversely connected, the protection IC 130 can be protectedfrom being damaged.

The effectiveness of the current restriction is so large that theresistance of the resistor R4 is high. However, the originalcommunication function of the protection IC 130 may be affected if theresistance of the resistor R4 is too high. It is preferred that theresistance of the resistor is on the order of several kΩ, which dependson the communication specification. When the resistor R4 is added as areverse charge protecting resistance in a case of the 1-linebidirectional communication specification, it is difficult to performhigh speed communication exceeding the speed of 100 kHz, and thecommunication specification on the order of several 10 kHz (bps) may beused.

<Example of Communication from Secondary Battery Monitoring IC 120 toProtection IC 130>

Next, with reference to FIG. 5 and FIG. 6, an example of thecommunication from the secondary battery monitoring IC 120 to theprotection IC 130 will be described.

FIG. 5 is a diagram for explaining the operation at the time of thecommunication from the secondary battery monitoring IC to the protectionIC in this embodiment. FIG. 6 is a diagram showing a list of commandsrecognized by the protection IC.

A fundamental operation of the protection IC 130 is to recognize acommand as shown in FIG. 6, at a time of a falling edge of the signal ofthe INT terminal as shown in FIG. 5, based on the output signal levelsof the CCNT terminal and the DCNT terminal. At a time of a rising edgeof the signal of the INT terminal, the output signal levels of the DCNTterminal and the CCNT terminal are disregarded.

In the example of FIG. 5, after the CCNT (PORT0) terminal is set to “0”and the DCNT (PORT1) terminal is set to “0”, the pulling down of the INT(PORT2) terminal is performed. At the time of a falling edge of thesignal of the INT terminal, the protection IC 130 latches the CCNTterminal and the DCNT terminal.

As in the command list of FIG. 6, the example of FIG. 5 is a case ofDCNT=0 and CCNT=0, and the secondary battery monitoring IC 120 outputs acompulsive FET control cancellation command for compulsively cancelingthe control of the FET in the protection IC 130, to the protection IC130.

According to FIG. 6, the secondary battery monitoring IC 120 outputs, inthe case of DCNT=0 and CCNT=1, a command for compulsively shifting theDOUT terminal from a high level (H) to a low level (L) to the protectionIC 130. In the case of DCNT=1 and CCNT=0, a command for compulsivelyshifting the COUT terminal from a high level (H) to a low level (L) isoutput to the protection IC 130.

In the case of DCNT=1 and CCNT=1, the secondary battery monitoring IC120 outputs an inquiry command for asking the protection IC 130 of theprotecting detection state (which is an operating state of theprotection IC 130) to the protection IC 130.

When the compulsive control of the DOUT/COUT terminals is performedafter the above-described command is received, the protection IC 130performs overwrite control to the DOUT terminal and the COUT terminal(which control is internally considered an OR logic). When the receivedcommand is the inquiry of protecting detection state, the protection IC130 sends a notification signal (command) indicating the protectingdetection state thereof as shown in FIG. 7, to the secondary batterymonitoring IC 120.

As described above, the secondary battery monitoring IC 120 performs thefunction for compulsively turning off the MOS transistors M11 and M12which are the charge control FET and the discharge control FET in theprotection IC 130, and performs the function for canceling thecompulsive turning off of the MOS transistors in the protection IC 130.The secondary battery monitoring IC 120 performs the function for askingthe protection IC 130 of the protecting detection state thereof.

<Example of Notification of Protecting Detection State of Protection IC130 to Secondary Battery Monitoring IC 120 when Inquiry Command isReceived from Secondary Battery Monitoring IC 120>

Next, with reference to FIG. 7, an example of notification of aprotecting detection state of the protection IC 130 (operating state)from the protection IC 130 to the secondary battery monitoring IC when aprotecting detection state inquiry command is received from thesecondary battery monitoring IC 120 the protection IC 130 will bedescribed. FIG. 7 is a diagram showing a notification command of aprotecting detection state of the protection IC sent to the secondarybattery monitoring IC.

In this embodiment, the protection IC 130 acquires the state of thelogic circuit 136 when the protecting detection state inquiry command isreceived at the communication control circuit 138. After the state ofthe logic circuit 136 is received, the protection IC 130 sets up theCCNT terminal 149 and the DCNT terminal 150 according to the protectingdetection state thereof. The terminal setting signal is predetermined toindicate the protecting detection state of the protection IC 130, suchas overcharge detection, discharge overcurrent detection, chargeovercurrent detection, as shown in FIG. 7.

For example, as shown in FIG. 7, in the case of DCNT=0 and CCNT=0, theprotection IC 130 outputs a command indicating no error (normalcondition) to the secondary battery monitoring IC 120. In the case ofDCNT=0 and CCNT=1, the protection IC 130 outputs a command indicatingthe discharge overcurrent detection state to the secondary batterymonitoring IC 120.

In the case of DCNT=1 and CCNT=0, the protection IC 130 outputs acommand indicating the charge overcurrent detection state to thesecondary battery monitoring IC 120. In the case of DCNT=1 and CCNT=1,the protection IC 130 outputs a command indicating the overchargedetection state to the secondary battery monitoring IC 120.

As described above, the protection IC 130 performs the function fornotifying the protecting detection state of the protection IC 130 inresponse to the protecting detection state inquiry from the secondarybattery monitoring IC 120.

<Example of Communication from Protection IC 130 to Secondary BatteryMonitoring IC 120>

Next, with reference to FIGS. 8, 9 and 10, some examples of operation atthe time of the communication from the protection IC 130 to thesecondary battery monitoring IC 120 will be described.

FIG. 8 is a diagram for explaining the operation at the time of thecommunication from the protection IC to the secondary battery monitoringIC when an undesired state of the secondary battery other thanoverdischarge is detected. In the case of FIG. 8, the logic of CCNT(PORT0) and DCNT (PORT1) denotes the state of these terminals when acharge overcurrent state of the secondary battery is detected. FIG. 9 isa diagram for explaining the operation at the time of the communicationfrom the protection IC to the secondary battery monitoring IC when anoverdischarge state of the secondary battery is detected. FIG. 10 showsa list of the commands recognized in the secondary battery monitoringIC.

The operation performed by the protection IC 130 in the case ofdetection of the battery overdischarge is different from that in thecases of detection of the battery overcharge and overcurrent other thanthe battery overdischarge. Specifically, in the cases of detection ofthe battery overcharge, discharge overcurrent and charge overcurrent,other than the battery overdischarge, the protection IC 130 sets theCCNT terminal and the DCNT terminal according to the command list ofFIG. 10 and outputs a pulse signal to the INT terminal.

As shown in FIG. 8, when overcharge of the secondary battery isdetected, the protection IC 130 sets the CCNT (PORT0) terminal to a lowlevel (0), sets the DCNT (PORT1) terminal to a high level (1), andthereafter outputs a pulse signal with a low level to the INT (PORT1)terminal for a fixed time. Subsequently, the protection IC 130 sets theCCNT (PORT0) terminal in an open state (high level).

The secondary battery monitoring IC 120 receives a falling edge of thepulse signal from the INT terminal as a trigger, and latches the CCNTterminal and the DCNT terminal. For example, the pulse width of thesignal from the INT terminal is set to MIN=100 microseconds, in order toensure the latching at 38.4 kHz.

As shown in FIG. 9, when overdischarge of the secondary battery isdetected, the protection IC 130 sets the CCNT (PORT0) terminal to a lowlevel, sets the DCNT (PORT1) terminal to a low level, and pulls down theINT (PORT1) terminal (or sets the INT (PORT1) terminal to a low leveland holds the same).

As shown in FIG. 10, in the case of DCNT=0 and CCNT=0, the protection IC130 notifies a command of overdischarge detection to the secondarybattery monitoring IC 120. In the case of DCNT=0 and CCNT 1, theprotection IC 130 notifies a command of discharge overcurrent detectionto the secondary battery monitoring IC 120. In the case of DCNT=1 andCCNT=0, the protection IC 130 notifies a command of charge overcurrentdetection to the secondary battery monitoring IC 120. In the case ofDCNT=1 and CCNT=1, the protection IC 130 notifies a command ofovercharge detection to the secondary battery monitoring IC 120.

After overdischarge of the secondary battery is detected and the DOUTterminal is set to the low level, the protection IC 130 maintains theINT (PORT2) terminal at the low level, turns off the voltage regulator131 that supplies the voltage to the secondary battery monitoring IC120, and thereafter sets the INT (PORT2) terminal in a HiZ(high-impedance) state. Because the voltage regulator 131 is turned off,the output signal is apparently kept at the low level.

As described above, the protection IC 130 is arranged to perform aninterrupt process to notify the secondary battery monitoring IC 120 ofthe information indicating that one of overcharge, overdischarge, chargeovercurrent, discharge overcurrent, etc. of the secondary battery isdetected.

The secondary battery monitoring IC 120 and the protection IC 130 usethe two-way communication interface of three lines to perform theabove-described function. One of the three lines is an interrupt signalline which is used to send an interrupt signal to the other device whenthe devices are in a communication state. The remaining lines are usedto send the information of the contents of the communication.

The secondary battery monitoring IC 120 and the protection IC 130 usethe two-way communication interface of three lines to perform theabove-described function. Alternatively, when extending further theabove-described function, the number of lines may be increased ifneeded, and the two-way communication interface of 4 or more lines maybe used.

<Example of Battery Pack Including Protection Monitoring Circuit, andMobile Device Including Battery Pack>

Next, with reference to FIG. 11, a battery pack 100 including aprotection monitoring circuit 101 of an embodiment of the presentdisclosure as well as a mobile device 160 in which the battery pack 100is arranged will be described. FIG. 11 shows an example of a batterypack including the protection monitoring circuit of this embodiment anda mobile device in which the battery pack is arranged.

As shown in FIG. 11, the protection monitoring circuit 101 of thisembodiment is contained in the battery pack 100. The battery pack 100including the protection monitoring circuit 101 is installed in themobile device 160.

As described above, according to the present disclosure, the secondarybattery monitoring circuit can compulsively operate the protectioncircuit, thereby providing a duplicate protection function for increasedsafety when overcharge, overcurrent, overdischarge, etc. of the batterypack is detected. For example, the voltage monitoring by the secondarybattery monitoring circuit can provide good accuracy of the detectionvoltage.

Moreover, according to the present disclosure, the secondary batterymonitoring circuit can request, at arbitrary timing, receiving of anoperating state of the protection circuit from the protection circuit.Hence, the secondary battery monitoring circuit can detect whether theprotecting operation is continuously performed by the protectioncircuit.

According to the present disclosure, when the protection circuit hasoperated, the secondary battery monitoring circuit is caused to performan interrupt process for outputting information indicating that theprotection circuit has operated, so that the log information of theprotecting operation can be stored in the secondary battery monitoringcircuit.

As described above, the secondary battery monitoring circuit cancertainly store the log information of the protecting operation by theprotection circuit for protecting the secondary battery. Based on thelog information of the protecting operation read from the battery pack,the use of the battery pack may be stopped, the charging of the batterypack may be inhibited, or exchange of the battery pack with a newbattery pack may be requested to the user of the mobile device.

Therefore, even if a problem of the battery pack, such as bulging orheating, occurs, reading the log information of the protecting operationfrom the battery pack at a local sales office makes it possible todetermine whether the problem of the battery pack is caused by a normaloperation or an erroneous operation of the user. In other words, the loginformation may be used as effective information for testing of thebattery pack under fault conditions.

The present disclosure is not limited to the above-describedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to a protection monitoring circuit,a battery pack, a secondary battery monitoring circuit, and a protectioncircuit.

What is claimed is:
 1. A protection monitoring circuit comprising: aprotection circuit which detects at least one of overcharge,overdischarge, and overcurrent of a secondary battery, and a secondarybattery monitoring circuit which monitors a state of the secondarybattery and detects a residual quantity of the secondary battery;wherein the protection circuit includes: a first communication terminalthat is connected to the secondary battery monitoring circuit, a secondcommunication terminal that is connected to a mobile device, and a levelshift circuit that is connected to the first and second communicationterminals, wherein the level shift circuit is configured to: perform alevel shift of a signal input of the first communication terminal so asto become a second level and output the signal to the secondcommunication terminal, and perform the level shift of a signal input ofthe second communication terminal so as to become a first level andoutput the signal to the first communication terminal.
 2. The protectionmonitoring circuit according to claim 1, wherein the protection circuitincludes an integrated circuit that is formed so as to have a highpressure resistance, and wherein the secondary battery monitoringcircuit includes an integrated circuit that is formed so as to have apressure resistance less than that of the protection circuit.
 3. Theprotection monitoring circuit according to claim 1, wherein the firstlevel is a power supply voltage level of the secondary batterymonitoring circuit, and wherein the second level is a power supplyvoltage level of the mobile device.
 4. The protection monitoring circuitaccording to claim 1, wherein the secondary battery monitoring circuitsends information data to and receives the information data from mobiledevice through the first communication terminal, the level shift circuitand the second communication terminal.
 5. The protection monitoringcircuit according to claim 1, wherein the level shift circuit isconfigured to perform a bilateral level shifting between the first andsecond communication terminals.